We no longer reference "background.js", because now we're going to handle the extension's logic in the popup's script (you are allowed background.js as well as a popup, it's just that we don't need it in this case).

We've added "browser_style": true, which will help the styling of our popup look more like part of the browser.

Finally, we've added "default_popup": "popup/choose_page.html", which is telling the browser that this browser action is now going to display a popup when clicked, the document for which can be found at "popup/choose_page.html".

So now we need to create that popup. Create a directory called "popup" then create a file called "choose_page.html" inside it. Give it the following contents:

In our JavaScript, we listen for clicks on the popup choices. We first check to see if the click landed on one of the page-choices; if not, we don't do anything else. If the click did land on a page-choice, we construct a URL from it, and open a new tab containing the corresponding page. Note that we can use WebExtension APIs in popup scripts, just as we can in background scripts.